That depends. Something like HDR should be able to fall back to non-HDR since it largely just adds data, so if the format specifies that extra information is ignored, there's a chance it works fine.

Probably most notably the iOS photos app until like 2014.

Edit: just checked. iOS 11 in 2017 added gif support to photos

I’ll also add, safari supported animated gifs for a long time before that and you could still save them in safari like any other image. But photos would only show the first frame like you said. When 11 came out they played like normal.

One example is piefed unfortunately. Animated gifs as avatar or banner don't animate currently as far as I can tell.

Those are displayed in browser, right? The only reason that would be happening is if Piefeed is recompressing images and their code is not smart enough to identify an animated .gif and act accordingly.

Yeah in browser. I should probably open an issue ticket if nobody else noticed yet.

I'll bet you a shiny penny that's what it is. The backend recompresses things to some other format, probably a low bitrate JPEG, in order to save space and/or in case some joker uploads a 90 megabyte uncompressed TIFF image to use as a profile pic, or something.

Lies! That gif is sped up 2000%!

I'm probably gonna be massively downvoted for saying the forbidden word but I asked AI to do a summary with references of the forward and backward compatibility of PNG's new version:

!

Based on recent search results, the new PNG specification (Third Edition) and its reference library (libpng) maintain strong backward compatibility while introducing modern features. Here's a detailed compatibility analysis:

1. Backward Compatibility (Viewing Old PNGs with New Lib)

• Full Support: The new libpng (1.6.49+) and PNG Third Edition fully support legacy PNG files. Existing PNGs (conforming to the 2003/2004 spec) will render correctly without changes .
• Implementation Stability: Libpng's API evolution (e.g., hiding png_struct/png_info internals since 1.5.0) ensures older apps using png_get_*/png_set_* functions remain compatible. Direct struct access, deprecated since 1.4.x, may break in libpng 2.0.x (C99-only) .
• Security Enhancements: Critical vulnerabilities (e.g., CVE-2019-7317 in png_image_free()) were patched in libpng 1.6.37+, making the new lib safer for decoding old files .

️ 2. Forward Compatibility (Viewing New PNGs with Old Lib)

• Basic Support: Older libpng versions (pre-1.6.37) can decode new PNGs if they avoid new features. Core chunks like IHDR or IDAT remain unchanged .
• New Feature Limitations:
  • HDR Imagery: Requires libpng 1.6.45+ and apps supporting the mDCv chunk. Older libs ignore HDR data, falling back to SDR, which may cause color inaccuracies .
  • APNG Animation: Officially standardized in PNG Third Edition. Older libs (e.g., <1.6) treat APNG as static images, showing only the first frame .
  • EXIF Metadata: New eXIf chunks are ignored by legacy decoders, losing metadata like GPS or copyright info .
• Security Risks: Older libs (e.g., ≤1.6.36) contain unpatched vulnerabilities (e.g., CVE-2015-8126). Parsing malicious new PNGs could exploit these flaws .

Compatibility Summary

Scenario	Compatibility	Key Considerations
Old PNG → New Lib	Excellent	Legacy files work flawlessly; security improved.
New PNG → Old Lib	️ Partial	Basic rendering works, but HDR/APNG/EXIF ignored. Security risks in unpatched versions.
New Features	Conditional	Requires updated apps (e.g., Photoshop, browsers) and OS support .

3. Implementation and Industry Adoption

• Broad Support: Major browsers (Chrome, Safari, Firefox), OSs (iOS, macOS), and tools (Photoshop, DaVinci Resolve) already support the new spec .
• Progressive Enhancement: New features like HDR use optional chunks, ensuring graceful degradation in older software .
• Future-Proofing: Work on PNG Fourth Edition (HDR/SDR interoperability) and Fifth Edition (better compression) is underway .

Conclusion

• Upgrade Recommended: New libpng (1.6.49+) ensures security and full compatibility with legacy files.
• Test Workflows: Verify critical tools handle new features (e.g., APNG animation in browsers).
• Fallbacks for Old Systems: For environments stuck with outdated libs, convert new PNGs to legacy format (e.g., strip HDR/APNG) .

For developers: Use png_get_valid(png_ptr, info_ptr, PNG_INFO_mDCv) to check HDR support and provide fallbacks .

!<

I see, but the animation feature cant be compatiable no?

downvoters: is it wrong?

And the crawling of flash websites is awful

As you can see it's irrelevant apparently. If it's AI generated it will be downvoted.

I don't know. If the poster couldn't be bothered to fact-check, why would I? It is just safer to assume that it can be misinformation.

Considering it named CVE-2019-7317, which was fixed in April 2019, it's already hallucinating and not worth reading further into it.

2029 Headline: Worlds largest data breach caused by zero day exploit in popular PNG 3.0 renderer

the payload was reportedly embedded in an animated image of the attacker repeatedly flicking his left testicle

I still miss using my iPAQ h4350. It still works; might be time to fire up Doom4CE...

LOL, I heard that gif. Timed it in my mind, on the money OP.

I have a Dell Axim X50v in a box somewhere. I imagine the battery is toast and I'll probably have to keep it in its cradle to remain powered. It was a hell of a machine for it's day.

I went through a succession Windows CE/PocketPC machines back in the day, starting with a Casio Cassiopeia E-115, then an Audiovox Maestro which was a rebadged Toshiba, then an HP iPAQ 2215, and finally the Axim.

The displays on the Maestro and the Axim were really something, and I wish someone would bring these back for a modern smartphone. They were rotten at color accuracy, but both had transflective displays that were fully readable even in direct sunlight. The Axim X50v also had a full 480x640 screen resolution which blew the first few iPhones out of the water on pixel density and even gave the iPhone 4 a run for its money. "Retina" display, my ass.

I had a Microdrive bunged into the CompactFlash slot on my Axim which was... several gigabytes, I don't remember how many. I kept it packed with MP3's, and I had a custom wallpaper with a white-on-chartreuse silhouette of a pacifier on it with the legend, "All 10,000 Songs On Your iPod Suck."

But then the entire PDA market got swallowed in one gulp by smartphones.